Optoelectronic transceiver modules provide for the bidirectional transmission of data between an electrical interface and an optical data link. The module receives electrically encoded data signals which are converted into optical signals and transmitted over the optical data link. Likewise, the module receives optically encoded data signals which are converted into electrical signals and transmitted onto the electrical interface. Copper transceiver modules provide bidirectional transmission of data between two electrical devices.
Normally, the transceiver is mounted onto one of the circuit card assemblies of a host computer, input/output system, peripheral device, or switch. Therefore, as with all electronic equipment, there is a need for a transceiver having an outer package design which occupies as little circuit card surface area as possible.
The gigabit interface converter (GBIC) specification was developed by a group of electronics manufacturers to arrive at a standard small form factor transceiver module for use with a wide variety of serial transmission media and connectors. The specification defines the electronic, electrical, and physical interface of removable serial transceiver module designed to operate at a giga-bit speed. A GBIC provides a pluggable module which may be inserted and removed from a host or switch chassis without powering off the receiving socket. The GBIC specification allows a single standard interface to be changed from a first serial medium to an alternate serial medium by removing a first GBIC module and plugging in a second GBIC having the desired alternate media interface.
According to the GBIC specification, the connection of the GBIC to the circuit board in the host enclosure (the host board) is identical for all implementations, regardless of external media type. For example, a GBIC with a DB9 connector can be replaced with a GBIC with an Single Connector (SC) duplex media connector. The mechanical form factor of the GBIC with reference to the host board is always the same. While not requiring a fixed form factor guide-rail or slot, common components are available that will suffice for most applications. Special socketing components can be built as required. Every GBIC will fit into a socket designed for any other GBIC. Further, the power interface includes two guide tabs integrated into the connector structure. The guide tabs shall be connected to circuit ground on both the host and GBIC. If the Transmitting Ground (TGND) and Receiving Ground (RGND) pins are separated on the GBIC, one guide tab shall be connected to TGND and the other to RGND. The guide tabs shall engage before any of the connector pins. This harmlessly discharges any stray static. The connector itself has two stages of contact sequencing, sequence stage 1 making contact before sequence 2 during insertion. Grounds and certain signals make contact in sequence stage 1. Power makes contact in stage 2. FIG. 1 shows the sequence of connections including the pin name, pin number, and the sequence of connection. When the GBIC is plugged in to a host circuit board, the numeral `1` denotes pins which make contact before pins denoted by numeral `2.` It may be noted that a preliminary step before stage 1 occurs when the GBIC external surface contacts the face plate opening or ground tabs of the receptacle of the host device in order to discharge static to chassis ground.
When a GBIC is hot plugged, several of the signal lines are connected at the same time as the power Vdd. This can cause a dangerous situation, especially with a GBIC having a module definition "4" which uses a Complementary Metal Oxide-Silicon (CMOS) serial EEPROM. The data and clock lines of the (Version 2) (SCA2) Electrically Erasable Programmable Read-Only Memory (EEPROM) Single Connector Attachment are connected through an connector. Connecting these signal lines to the EEPROM at the same time as Vdd can cause this EEPROM to malfunction or even be destroyed, and with it the GBIC.